Catalytic ozonation of real textile wastewater by magnetic oxidized g-C3N4 modified with Al2O3 nanoparticles as a novel catalyst

Abstract

• The graphitic carbon nitride was oxidized by a novel method. • The BET surface area increased from 57.31 to 115.41 m 2 /g after Al 2 O 3 immobilization. • Catalytic ozonation using O@g-C 3 N 4 /Al 2 O 3 nanocatalyst resulted in 75% COD removal. • Textile wastewater effluent resulted in meeting EPA discharge criteria. • BI enhanced from 0.27 to 0.74 after 60 min of catalytic ozonation. Textile wastewater has been known for its high resistance toward conventional wastewater treatment because of its low biodegradability index (BI). In this study, the catalytic ozonation of real textile wastewater has been carried out using a novel magnetic oxidized g-C 3 N 4 / Al 2 O 3 (O@g-C 3 N 4 / Al 2 O 3 ) nanocatalyst. The effect of Al 2 O 3 content on the catalytic activity of nanocatalyst was investigated, and the results marked that the nanocomposite with the equal mass ratio of Al 2 O 3 to magnetic oxidized g-C 3 N 4 had the best performance. The material characterization was investigated using Field-Emission Scanning Electron Microscopy (FESEM), Vibrating Sample Magnetometer (VSM), X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR), and Brunauer-Emmett-Teller (BET) analysis, respectively. The effect of pH, catalyst dosage, and oxygen flow rate were studied, and the maximum performance was achieved at a pH of 7.1, the oxygen flow rate of 1.5 L/min, and the catalyst dosage of 0.5 g/L. The ozonation kinetics plots of the single ozonation process (SOP) and catalytic ozonation process (COP) showed two different linear parts. The rate of COD removal was much greater in the first 5 min of ozonation because of oxidation of easily degradable compounds. Furthermore, the rate constant of COP after 5 min of ozonation was four times higher compared to that of SOP, indicating the greater potential of COP toward oxidation of recalcitrant compounds. However, the rate constant in the first 5 min of COP was only two times greater than that of SOP, which is a result of oxidation of easily degradable compounds. The COD and color removal of 77% and 99% and BI of 0.74 were attained in 60 min in the COP process. However, treated wastewater resulted in 127 mg/L residual COD of initial wastewater after catalytic ozonation meeting EPA standards discharge for textile and dyeing industry effluent. The results of regeneration experiments indicated that the COD removal decreased only about 8% after five regeneration cycles.